Intermolecular Hydrogen Bonding between Water and Pyrazine

Completely planar is the hydrogen-bonded complex of pyrazine and water (see sketch), which was obtained by supersonic expansion and investigated by rotational spectroscopy. The water molecule lies in the plane of the aromatic ring, and the lone pair of electrons on the nitrogen atom functions as the acceptor in the N???H-O hydrogen bond, not--as in the corresponding benzene complex--the ? electrons.